Electrodeposition of organic materials on anodes from aqueous emulsions thereof



June 15 1926. 1,589,324

IALS on moans QUEOUS amunsxous THEREOF Filed May 7. 1925 C. L. BEAL El AL ELECTRODEPOSITION OF ORGANIC MATER FROM A INVENTORS,

Carl LBeaL w zd/ Leon WEberZuv,

"lllllllllllllllln A TTORNEYI Patented June 15, 1926.

UNITED STATES 1,589,324 PATENT OFFICE.

CARL L. BEAL AND LEON W. EBERLIN, OF ROCHESTER, NEW YORK, ASSIGNORS TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

ELECTRODEPOSITION OF ORGANIC MATERIALS ON ANODES FROM AQUEOUS EMUII' SIONS THEREOF.

Application filed May 7, 1925. Serial No. 28,690.

This invention relates to the electrodeposition of organic materials such, for instance, as rubber and cellulosic compounds, upon anodes from aqueous emulsions thereof. One object of the invention is to provide an improved process of this nature which will minimize any harmful effects due to nascent oxygen liberated at the anode. Another object of the invention is to provide such a process in which polarization oxygen at the anode is counteracted. till a further object of the invention is to provide a process in which the oxidized compounds formed at the anode will be compatible with the substances deposited at that place. Other objects will hereinafter appear.

In the accompanying drawings, forming a part hereof, F1 1 to 3 are diagrammatic cross sections 0 different forms of apparatus which may be employed in carrying out our process.

In the electrodeposition of organic m ate-' rials on anodes from aqueous emulsions thereof, such as aqueous emulsions of rubber or cellulosic compounds, like nitrocellulose, acetyl cellulose, and cellulose ether, the coatings sometimes oxidation from nascent oxygen liberated at the anode when high current densities are employed. Moreover, under these conditions the process is apt to be slowed down by polarization at the anode, due to liberated oxygen. Of course, bubbles of oxygen tend to spoil the continuity and smoothness of the deposit.

We have found that these difficulties can be wholly overcome or very largely avoided by having present in the anode zone, durlng the deposition, a metal which has-a greater aflinity for nascent oxygen than the deposited organic material has.. By the anode zone we mean the zone in which nascent oxygen is liberated; and by nascent oxygen we refer to electrolytically liberated atomic oxygen which is known to be especially active. zinc, cadmium and magnesium. They are unusually efiective when rubber is electrodeposlted. Any of them will strongly protect the rubberfrom injury by oxidation and will counteract polarization by combining with the oxygen at the anode. This results in few, if any, bubbles of oxygen to become impaired by Examples of suitable metals are impair the continuity and smoothness of the rubber deposit. Moreover, the oxides of these metals, which are formed at the anode, are all compatible with the rubber and form useful fillers in the final composition.

We can have. the desired metal, such as zinc, for example, in different forms at the anode zone. For instance, the anode surface upon which the organic material is to be deposited may be coated with the metal, or the whole artlcle upon which the anodesurface is located, may be of the desired'metal, such as zinc or a zinc alloy. The metal may also be present in the droplets of the emulsion when the electrodeposition takes place. By way of illustration, we may prepare dispersions or emulsions of the desired metal with the aid of protective colloids and combine them with t e aqueous emulsions of organic materials such as rubber emulsions. Still a different way of bringing the metal to the anode zone is to have it suspended in a porous or conducting coating over the surface upon which the deposit is to be made. Thus a mixture of gelatin and zinc powder may be thinly painted over the electroconducting surface to be treated.

Our process ma be used as an improvement upon or auxi iary to the electrodepositing processes disclosed in U. S. Patent No. 1,476,374, Samuel E. Sheppard and Leon W. Eberlin, Dec. 4, 1923, for electrodeposition of rubber coatings, and copending a plications Serial No. 21,311, filed April 1925, Leon "W. Eberlin and Carl L. Beal, for electrodeposition of coatings of cellulosic compounds, and Serial No. 21,341, filed April 7, 1925, Samuel E. Sheppard and Leon WV. Eberlin, for electrodeposition of coatings comprising rubber and a cellulosic compound. Obviously the principle of our invention is adaptable to the production of coatings wherever oxygen is liable to cause harm when electrodeposition takes place at an anode from aqueous emulsions or similar dispersions.

We shall now describe, by way of illustration, the preferred embodiment of our invention, but it will be understood that the latter is not limited to the details given, except as indicated in the appended claims.

We prefer to employ any of the rubbercontaining emulsions disclosed in the above cited patent and applications or in application Serial No. 611,162, Samuel E. Sheppard and Leon W. Eberlin, filed Jan. 6,1923, for rubber emulsion and process of making the same, and application Serial .No. 21,340, Samuel 'E. Sheppard and Leon W. Eberlin, filed April 7, 1925, for aqueous emulsion of unvulcanized rubber and sulfur. The emulsions of the latter application are very dependable in their properties.

The particles in all of the above mentioned emulsions act as ifnegatively charged, and travel toward the anode. Referring to Fig. 1, the electroconducting face 1 of the object to be plated is covered with a thin layer or coating 7 of a suitable metal, such as zinc. This coating may be applied by any of the usual known or preferred zinc plating methods. The coated face is then connected'at 2 to anode line 3 so as to form the anode and is immersed in the emulsion 4. A suitable cathode is also placed in contact with the emulsion. For instance, the latter may be contained in a metal vessel 5 which is connected in the cathode circuit 6.

The current should preferably be an effectively unidirectional one. It may be a current of constant value or a direct current of pulsating character. In some instances it is useful to employ an unbalanced alternating current, which is most conveniently obtained by superimposing an alternating current upon a direct current. The voltages and current densities to be employed can vary over a considerable range. Higher current densities can be employed w1th greater safety because of the presence of our oxidizable metal in the anode zone. Since direct currents of 110 volts are conveniently available, we prefer to use them and regulate the corresponding density to about A to of an ampere per square inch of electrode sur: face to be coated. In general the plating expedients follow the practice given 1n the patents hereinabove cited.

Referring to Fig. 2, the electroconducting surface 1 to be plated is part of a body composed wholly of zinc or zinc alloy. It is, therefore, ready to receive an electrodeposited coating .from aqueous emulsion of rubber 4, it being connected at 2 to anode line 3, vessel 5 being the cathode which is connected to line 6.

Referrin to Fig. 3 the face 1, of the article to be p ated, is coated with a substratum 17 composed of gelatin or glue carrying a powder or pigment of metallic zinc or magnesium. The substratumed article is then connected at 2 to anode line 3 and is immersed in the electroconducting aqueous rubber emulsion 4. The vessel 5 may serve as a cathode and is connected to the cathode line 6. The use of a substratum for the production of an even coating is not claimed herein, this being covered in the application of Samuel E. Sheppard and Carl L. Beal, Serial No. 25,160, filed April 22, 1925, for electrodeposition of organic materials such as rubber and cellulosic compounds. In our present illustration the substratum not only serves to insure an even coating, but serves as a vehicle for holding our oxidizable metal in the anode zone.

In all of the above examples, nascent oxygen is liberated as the anode and attacks the metal much more rapidly than it does the rubber. Where the emulsion comprises natural latex, the final deposit has the least possible degradation, as is evidenced by its very high mechanical strength. It has no degradation due to mechanical milling and little, if any, degradation due to chemical oxidation in the plating operations. Moreover, zinc oxide and magnesium oxide, (or cadmium oxide if the latter rarer metal is used) are well known fillers for rubber compositions and, therefore, blend properly into the coating of rubber, even when the latter is vulcanize During the electrodeposition, particularly with the arrangements illustrated in Fi 1 and 2, the zinc, or equivalent metal, dissolves reversibly, that is electrolytically, and then combines with the oxygen. It is, therefore, not liable to passivity.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The process of de ositing or anic material on an electrocon ucting surfiace of an object, which comprises bringing said surface, connected as an anode, into contact with an aqueous electroconducting emulsion of said or anic material and passin a depositing e ectric current through said surface and emulsion, there bein present in the anode zone duringhe deposition a metal having a greater a ity for oxygen than said orgamc material has.

2. The process of depositing rubber on an electroconducting surface of an object, which comprises bringin said surface, as an anode, into contact wit an aqueous electroconducting emulsion of rubber and passing a depositing electric current through said surface and emulsion, there being present in the anode zone during the deposition a metal having a greater aflinity for oxygen than rubber has, and the oxide of said metal being compatible with rubber in the deposit.

3. The process of depositing organic material on an electroconducting surface of an object, which comprises bringing said surface, connected as an anode, into contact w1th an aqueous electroconducting emulsion of said organic material and passing a depositing electric current through said surface and emulsion, there being present in the anode zone during the deposition suflicient zinc to take up liberated oxygen.

4. The process of depositing rubber on an electrooonducting surface of an object, which comprises bringing said surface, as an anode, into contact with an aqueous electroconducting rubber emulsion and passing a depositing electric current through said surface and emulsion, there being sufficient zinc in the anode zone during the deposition to take up liberated oxygen.

5. The process of depositing organic material on an electroconducting surface of an object, which com rises covering said surface with a layer 0 a metal which has a greater afiinity for oxygen than said organic material has, bringing said covered surface into-contact with an aqueous electroconducting emulsion of said organic material and passing a depositing electric current through said surface, covering and emulsion.

6. The process of depositing rubber on an electroconducting surface of an object, which comprises covering said surface with a metal havlng a greater aflinity' for oxygen than rubber has, which counteracts polarization at the anode, bringing said covered surface into contactwith an equeous electroconducting rubber emulsion and passing a depositing electric current through said surface, covering and emulsion.

7. The process of depositing rubber on an electroconducting surface of an object, which comprises covering said surface with zinc, bringing said covered surface into contact with an aqueous electroconducting rubber emulsion and passin a depositing electric current through said surface, zinc covering and emulsion.

Signed at Rochester, New York, this 4th day of May 1925.

CARL L. BEAL. LEON W. EBERLIN. 

